Centrifugal pump

ABSTRACT

A centrifugal pump is proposed, in particular for household appliances, such as washing machines or dishwashers, with a pump housing, whose exterior shape is essentially radially symmetrical, and which has an axial inlet and a peripheral outlet, along with a rotatably mounted impeller, wherein a flow channel enveloping the impeller and heating element is provided. In such a centrifugal pump, the object is to increase the efficiency by having the flow cross-section of the flow channel ( 15 ) increase along the periphery toward the outlet.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention relates to a centrifugal pump, in particular for household appliances, which pump has a radially symmetrical shape having an axial inlet and a peripheral outlet. More particularly the novel pump has a rotatably mounted impeller having a flow channel increasing in size along the periphery toward the outlet.

(2) Description of the Related Art including Information Disclosed Under 37 C.F.R. 1.97 and 1.98

In household appliances, such as dishwashers or washing machines, centrifugal pumps are normally used to circulate the cleaning liquid.

The use of pumps with radially symmetrical, e.g., cylindrical, housings has proven advantageous for more easily combining centrifugal pumps with additional functional elements, e.g., heating elements or the like.

Such a housing shape is easier to manufacture in comparison to screw-shaped pump casings, in which the radius changes along the periphery, e.g., in an injection molding process. In addition, such a pump can be manufactured with a compact outer shape, so that it can also be used accordingly under confined spatial conditions.

Such pumps are described in publications DE 199 16 136 and DE 103 24 626 A1.

SUMMARY OF THE INVENTION

The objective of the invention is to propose a cylindrical centrifugal pump in which pump efficiency is improved relative to prior art.

This objective is achieved proceeding from a centrifugal pump having a substantially radially symmetrical exterior having an axial inlet and a peripheral outlet and an impeller and flow channel in which the cross section of the flow channel increases along the periphery toward the outlet.

The invention and its preferred embodiments further includes a flow channel having an upwardly sloping bottom, a continuous inlet gap in the interior of the flow channel with or without a uniform height, an annular gap at the inlet gap, a modified impeller that is smaller than or equal to the height of the gap, an axial inlet support, an optional heating element and the addition of the heating element into a groove of the pump housing, the disposition of the heating element on the side of the impeller facing the heating element and the matching of the impeller profile to the heating element.

Accordingly, a radially symmetrical centrifugal pump based on the invention is characterized in that a flow channel enveloping the impeller and heating element is provided, which increases along the periphery toward the pump outlet.

This measure makes it possible to tangibly increase the maximum volume flow, and hence the efficiency, of the centrifugal pump. A smaller centrifugal pump can hence be used, resulting in corresponding production and operation-related savings.

A pump housing is radially symmetrical or cylindrical within the meaning of this invention without taking into account the peripheral or tangential outlet, which naturally disrupts the symmetrical shape.

The exterior shape of the pump housing preferably has an essentially cylindrical design. The aforementioned advantages of a basic radially symmetrical shape, i.e., simpler production, are further improved in this embodiment, since the radius also remains constant over the height in a cylindrical shape.

In a further development of the invention, the flow cross section of the flow channel is increased by changing the axial dimension of the flow channel. This makes it possible to achieve a particularly compact pump.

In addition, the flow channel is provided with a sloped bottom in a special embodiment. Sloping the bottom, i.e., the end facing away from the heating element, of the flow channel makes it possible to influence the flow conditions, in particular at the transition to the outlet. Outwardly increasing the inclination of this channel bottom enables a smooth transition in the outlet without any flow-disrupting offset, for example.

The interior of the flow channel is advantageously provided with a continuous inlet gap, which has an essentially constant height in a preferred embodiment. This step makes it possible to improve the flow conditions, and hence the efficiency, of the pump. In particular, the so-called dead volume can be limited in this way.

These advantages are achieved in particular in combination with an impeller having an annular gap lying at the height of the inlet gap of the flow channel. The height of this annular gap is preferably designed to be smaller than or equal to the height of the continuous inlet gap described above. The liquid pushed to the outside by centrifugal forces from the rotating impeller is here forced directly into the flow channel, wherein corresponding impeller blades impart not just a radial motion to the liquid, but also a circulating flow. The rising rotational radius of the cleaning liquid caused by centrifugal forces given an identical angular velocity due to exposure to the impeller blades additionally increases the velocity, and hence volume throughput.

To further improve pump efficiency, the impeller is preferably provided with an increasing volume in an axial direction. The impeller has a specific interior volume due to an upper and lower cover with blade elements lying in between, and its efficiency increases as does the volume of liquid that can be processed by the impeller. The volume in the impeller along with the impeller shape (in particular the blade shape) determines the energy conversion in the impeller.

In particular, in conjunction with the aforementioned features aimed at further developing the invention, an impeller widened in an axial direction is advantageous, since the pump housing has a corresponding volume in this direction for receiving an impeller enlarged in this way, owing to the increased axial dimension of the flow channel. This measure makes it possible to improve the efficiency accordingly. The impeller volume can be increased in this way by a corresponding bulge, for example.

In addition, the pump inlet is provided with an inlet support in an advantageous embodiment, which extends into an inlet opening of the impeller. This improves the flow of the liquid to be conveyed into the impeller. Lateral flows are hereby prevented from passing by the impeller. The so-called dead volume of the pump is kept correspondingly low.

A pump according to the invention is preferably provided with a heating element. Such a heating element is here preferably arranged in such a way as to be separated from the interior space of the pump by a heat-conducting wall of the pump housing. In a radially symmetrical, in particular a cylindrical, pump housing, it is here especially easy to secure the heating element on the end of the pump housing. For example, to increase the efficiency of the heating element, a groove can be incorporated in the corresponding wall of the pump housing, e.g., a front cover, for this purpose.

Since the flow channel outwardly envelops not just the impeller, but also the heating element, the cleaning liquid to be heated necessarily flows over the heating element or its receptacle in the pump housing over a very large contact surface and at a high volume rate. This yields a good heating efficiency, which can as a result be brought into thermal contact with the cleaning liquid on over 75% of its surface, for example, or, given a corresponding cross sectional design, over an even greater percentage.

In a special embodiment of the invention, the heating element is arranged at least partially next to the impeller in an axial direction. This makes it possible to realize a flow channel with an axial dimension that allows it to envelop both the impeller and heating element, and permits the advantageous heating element flow described above.

In addition, it is preferred that the increase in the flow channel axial dimension be made on the side opposite the heating element along the periphery toward the outlet. This is advantageous in particular with the heating element arranged in an axial direction next to the impeller, since the heating element limits the number of ways the pump can be configured in the direction toward the heating element.

The heating element is advantageously arranged on the side of the impeller facing the axial inlet of the pump housing. In this way, the impeller drive can be actuated from the other side, without the drive and heating element or heating element connections having a disruptive influence.

In addition, the heating element advantageously has at least a partially annular design. Such a ring or partial ring can be concentrically applied to a face of the pump housing, so that the rotary flow inside the pump housing can be used to achieve a good flow toward the heating element or its receptacle in the pump housing. In particular, the rotary pump flow also enables the stream to pass over the outside of the heating element. In the embodiment described above, in which the heating element is arranged on the side of the impeller facing the axial inlet of the pump housing, the heating element thus at least partially envelops the axial inlet of the pump housing.

In a further development of the invention, the side of the impeller facing the heating element is matched to the profile of the heating element or its receptacle in the pump housing. This diminishes the dead volume on the one hand, and hence improves pump efficiency. On the other hand, the overall dimensions of the pump are kept low as a result.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

An embodiment of the invention is depicted in the drawing, and will be explained in greater detail below based on the figures.

Shown on:

FIG. 1 is a longitudinal section through a pump according to the invention,

FIG. 2 is a perspective, sectional view of a pump according to FIG. 1, and

FIG. 3 is a perspective, sectional view of another embodiment of a pump according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The pump 1 according to FIG. 1 comprises a cylindrical pump housing 2 having a cover 3 on its upper side. The cover 3 can accommodate the heating element not shown on FIG. 1, and to this end can be made out of a heat-conducting material, e.g., metal.

Located inside the pump housing 2 is an impeller 4, which essentially consists of a lower cover 5, 6 with blades 7 arranged in between. The blades 7 are curved and molded in such a way as go generate a corresponding annular flow of the liquid located in the impeller 4 as the impeller 4 rotates.

The bottom of the impeller 4 is provided with an axial projection 8, which is provided with a central hole 9 for accommodating a drive shaft (not shown in greater detail). The drive of the impeller 4 is hence actuated from the side opposite the heating element or the cover 3.

The top cover 5 has a central opening 10 into which the inlet support 11 extends. An outlet support 12 is placed behind the pump housing 2 in a tangential direction in the view according to FIG. 3.

The impeller 4 has an opening gap 13 on its edge, which lies opposite an inlet gap 14 of a flow channel 15 according to the invention at roughly the same height. The flow channel 15 extends at an axial height up to a groove 16 for accommodating the heating element, so that the liquid located in the flow channel 15 flows around the outside of not just the impeller 4, but also of the heating groove 16.

As evident from FIG. 1, the heating groove 16 is correspondingly in contact with the liquid located inside the pump housing 2 on three sides, and hence over distinctly more than 75% of the available contact surface based on the larger height in comparison to the width of the heating groove 16.

FIG. 1 clearly shows the different axial dimension h, H of the flow channel 15 on both sides of the sectional view. This different axial dimension h, H is manifested in a continuous peripheral increase in height h until reaching height H. This increase takes place continuously in the cut off front section of the pump (not shown in the view according to FIG. 1), and ends in the rearward area at the transition into the outlet support 12.

The bottom 17 of the flow channel 15 is upwardly sloped toward the outside. It also exhibits a slight bulge. This shape facilitates the transition into the outlet support 12, as explained further above.

The bottom cover 6 of the impeller 4 is bulged to the extent that it clearly extends into the space 18 below the inlet gap 14, thereby using this volume of the pump housing 2 to increase the interior volume of the impeller 4. The round bulge of the bottom cover 6 here in turn serves to improve flow inside the impeller 4, i.e., to guide the water toward the inlet gap 14 of the flow channel 15.

The contour of the top cover 5 is matched to the cover 3 or heating groove 16. This shape of the top cover 5 further ensures a sufficient intermediate space 18, 19 between the top cover 5 and the heating groove 16. In this intermediate space 18, 19, heat can consequently also be transferred to the liquid present there.

The view according to FIG. 2 essentially corresponds to the embodiment illustrated in FIG. 1. Readily discernible in this view is the transition 20 to the outlet support 12, which has a receptacle 21 for a pressure sensor. As opposed to FIG. 1, this view also shows a heating element 22 consisting of a heating rod that has been bent into a ring segment and inserted into the heating groove 16. The end of the heating element 22 is upwardly bent, providing a connection 23 for the heating element 22.

The heating element 22 is form fitted to the heating groove 16, and additionally connected there in a thermally conductive manner, e.g., by a soldered contact.

The embodiment according to FIG. 3 essentially corresponds to the pump described based on FIG. 2, the difference being that the bottom 24 of the outwardly running flow channel 25 is no longer sloped, but exhibits a round bulge. However, the increase in axial dimension h, H of the flow channel 25 is as readily discernible here as is the use of the interior space 27 available below the inlet gap 26 for increasing the volume of the impeller 28. 

1. A centrifugal pump, for household appliances, such as washing machines or dishwashers, having a pump housing, with a substantially radially symmetrical exterior having an axial inlet and a peripheral outlet, along with a rotatably mounted impeller, wherein the improvement comprises a flow channel enveloping the impeller said flow channel (15) having an increase in cross section along the periphery toward the outlet.
 2. The pump according to claim 1, wherein the pump housing has an essentially cylindrical exterior shape.
 3. The pump according to claim 1 wherein the axial dimension (h, H) of the flow channel (15) increases along the periphery toward the outlet (12).
 4. The pump according to claim 1 or 3 wherein the flow channel (15) has a bottom (17) that is upwardly sloped toward the outside.
 5. The pump according to claim 1 wherein the interior of the flow channel (15) is provided with a continuous inlet gap (14).
 6. The pump according to claim 1 wherein the continuous inlet gap (14) has an essentially constant height.
 7. The pump according to claim 1 wherein the impeller (4) has an annular gap (13) lying at roughly the height of the inlet gap (14) of the flow channel.
 8. The pump according to claim 7 wherein the height of the annular gap (13) of the impeller (4) is smaller than or equal to the height of the continuous inlet gap (14) of the flow channel (15).
 9. The pump according to claim 1 wherein the volume of the impeller (4) increases in an axial direction.
 10. The pump according to claim 1 further comprising a heating element and wherein the volume increase of the impeller (4) is arranged on the side of the impeller (4) facing away from the heating element (22).
 11. The pump according to claim 1 wherein the inlet comprises an axial inlet support (11) that extends into an inlet opening (10) of the impeller (4).
 12. The pump according to claim 1 further comprising a heating element (22).
 13. The pump according to claim 1 further comprising a heating element (22) wherein said heating element is separated from the interior space of the pump by a heat-conducting wall of the pump housing.
 14. The pump according to claim 1 further comprising a heating element wherein the heating element (22) is incorporated into a groove of the pump housing.
 15. The pump according to claim 1 further comprising a heating element wherein the axial dimension (h, H) of the flow channel (15) increases on the side opposite the heating element (22) along the periphery toward the outlet (12).
 16. The pump according to claim 1 further comprising a heating element wherein the heating element (22) is arranged on the side of the impeller (4) facing the axial inlet (11) of the pump housing (2).
 17. The pump according to claim 12 wherein the heating element (22) is of a substantially annular configuration.
 18. The pump according to claim 1 further comprising a heating element wherein the side of the impeller (4) facing the heating element (22) is matched to the profile of the heating element (22) or its receptacle (16) in the pump housing (2).
 19. The pump according to claim 1 wherein said pump is disposed in a washing machine or a dishwasher. 